Semiconductor chips such as a semiconductor memory are stacked in some cases from the viewpoint of high functionality or high integration. In order to electrically connect elements on the stacked semiconductor chips to each other, through electrodes called TSV (Through-Silicon Via) are used. A TSV passes through a substrate and electrically connects elements on the substrate and elements on another substrate together. In order not to affect the characteristics of the elements, the TSV is demanded to be low in the parasitic resistance and the parasitic capacitance.
Although the TSV itself is formed of a metal and has a low resistance, the aspect ratio of a contact hole for the TSV formed in the substrate is high. Accordingly, there is a problem that the contact area between the TSV and wires at the bottom of the contact hole is small and the contact resistance between the TSV and the wires is high.